1. Technical Field
The present invention relates to polarization conversion elements, polarization conversion units, projection apparatuses, and methods for manufacturing polarization conversion elements.
2. Related Art
Typically, a polarization conversion element that convers light of a light source into one type of polarized light is incorporated in a projection apparatus such as a projector. The polarization conversion element includes an element main body having a plurality of light-transmissive members with polarization separating films and reflection films alternately provided therebetween, and adhesive layers that are formed with adhesive between the plural light-transmissive members. Phase difference plates are selectively disposed on a light emission surface of the element main body (see, for example, JP-A-2000-298212 and Japanese Patent 3309846).
As shown in FIGS. 15 and 16, in fabricating the polarization conversion element described above, first, light-transmissive plate members with polarization separating films 91 and reflection films 92 formed thereon, and light-transmissive plate members without the aforementioned films formed thereon are alternately laminated with adhesive layers 93. The thickness of each of the adhesive layers 93 may reach, for example, about 20 μm. A laminate body of the laminated members is cut at a predetermined angle with respect to a surface of the laminated body to obtain an element main body. Then, cut surfaces of the element main body 95 are polished to form a light incident surface 951 and a light emission surface 952. Then, a phase difference plate 97 is bonded to the element main body 95 through a bonding layer 96.
However, for example, when the polarization conversion element described in JP-A-2000-298212 and Japanese Patent 3309846 is fabricated using adhesive of related art, the adhesive layer 93 would become thick as the adhesive has high viscosity. When the laminate body having such thick adhesive layers 93 is cut, strain would be generated at end sections of the adhesive layers 93. When the cut surfaces are polished with the strain being present, corner sections 981 of the light-transmissive members 98 near the adhesive layers 93 would be carved, as shown in FIGS. 15 and 16.
For example, if the bonding layer 96 is formed by a plasma polymerization method described, for example, in JP-A-2010-113056, some problems would arise. For example, a gap may be generated at the bonding layer 96 such that the phase difference plate 97 would likely be separated, and air bubbles may be formed in the bonding layer 96 such that its light transmissivity would be lowered. Also, if the phase difference plate 97 is bonded to the light emission surface 952A by adhesive, the area through which light is effectively transmitted becomes smaller because the corner sections 981 of the light-transmissive member 98 are cut near the adhesive layers 91.